Oxidation of petroleum



United States Patent OXIDATION OF PETROLEUM William B. Whitney, Bartlesville, 0kla., assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing. Application January 3, 1952, Serial No. 264,840

12 Claims. (Cl. 196-142) The invention relates to the oxidation of petroleum. In one of its more specific aspects, this invention relates to petroleum oxidation products. In another of its more specific aspects, this invention relates to oxidized petroleum products used as lubricating oil additives. In another of its more specific aspects, it relates to a method for obtaining lubricating oil additives of improved color from oxidized petroleum fractions. In another of its more specific aspects, it relates to a method for obtaining oxidized petroleum products of improved color.

The oxidation of a petroleum fraction so as to obtain high molecular weight products having excellent detergent value is disclosed in my copending U. S. application, Serial No. 264,839, filed January 3, 1952, now Patent No. 2,758,069 and Serial No. 304,659, filed August 15, 1952. The additive materials produced in this manner are quite black and impart a very undesirable color to the oil with which it is incorporated. The extent of the discoloration of the oil is of course dependent upon the amount of the black additive which is added to the lubricating oil.

By at least one aspect of this invention, at least one of the objects of this invention is obtained.

An object of this invention is to provide a method for obtaining oxidized petroleum materials which have a color improved over that previously known. Another object of this invention is to provide an improved method for obtaining higher molecular weight lubricating oil additives. Another object of this invention is to provide a method for producing lubricating oil detergents from highly refined petroleum bright stock. Another object of the invention is to provide a method for purifying highly refined petroleum bright stock so as to obtain oxidized products of that purified oil which have improved color and are suitable for use as detergents in lubricating oil.

Broadly speaking, this invention comprises oxidizing a petroleum fraction which has been purified by treatment with silica gel. The process includes the step of subjecting a petroleum bright stock which has been highly refined, such as by propane fractionation and phenol extraction to a purification step such as contact with silica gel. The petroleum fraction which is preferably used for the production of the oxidized product is one which is liquid and has a viscosity of between 70 and 700 Saybolt seconds at 210 F. It is preferred to utilize a fraction which has a viscosity in the range of 115 and 300 Saybolt seconds at 210 F. The oil which I use generally has a molecular weight within the range of between about 400 and 1100. During contact of the oil with the silica gel one unadsorbed oil fraction is obtained and a second fraction is obtained by desorbing the silica gel with pentane or some other saturated aliphatic hydrocarbon generally in the C5 to C7 range. The unadsorbed oil portion and the portion obtained in the initial desorption steps form the preferred fraction for oxidation to obtain the additive material of improved color. The wash liquid may be any saturated aliphatic hydrocarbon having a boiling point below that of the petroleum fraction. The percent of carbon atoms present in the aromatic rings in the preferred purified oil fraction is much smaller-than that present in the original unpurified petroleum bright stock. The preferred purified oil fraction is subjected to oxidation and the resulting oxidation products are recovered from the petroleum phase. Oxidation products obtained as a result of this process are red in colorand they do not unduly discolor the lubricating oil when incorporated therewith.

The purchasing public strongly resists the use of lubricating oils which have a comparatively black or dirty color. Although the quality of such oils is often very good, purchasers do not feel that they can be sure of obtaining a good oil when such oil has a black or dirty appearance. This invention provides a solution for the problem presented by trade resistance to incorporating dark colored materials in lubricating oils. I have discovered that the detergent characteristics provided by incorporating products obtained by oxidizing a hydrocarbon fraction are also provided by the oxidation of a petroleum bright stock which has been purified in the manner of this invention. The oxidation products which are obtained as a result of this purification step and the subsequent oxidation step together with conventional methods of recovery have a color which is much lighter than that obtained when an unpurified petroleum bright stock is subjected to oxidation.

According to the process of this invention, a highly refined oil, such as that which is obtained by propane fractionation and phenol extracting is subjected to purification, such as by contact with silica gel. The oil is normally diluted with a saturated aliphatic hydrocarbon in the C to C7 range and is passed through a mass of silica gel. That portion which comes through the gel in the initial pass and as the result of the initial desorption steps is the oil fraction which I use in the process of this invention. The oil which I use has, as stated above, a viscosity within the range of between 70 and 700 Saybolt seconds at 210 F. A preferred fraction for treatment and use in my process is one which has a viscosity within the range of between and 300 Saybolt seconds at 210 F. The oil stream is preferably subjected to the silica gel adsorption at a temperature approximating room temperature and generally at substantially atmospheric pressure or at suflicient pressure to cause oil in its diluted condition to flow through the mass of silica gel. Higher or lower temperatures may be utilized with a concomitant adjustment in pressure. Higher temperatures are not as desirable, however, for the reason that the higher temperature tends to reduce the capacity of the silica gel for adsorption of the undesired petroleum materials. In a continuous process, it is preferred to utilize a plurality of adsorption.

chambers so that a chamber can be taken off stream when the silica gel bed becomes saturated and can be regenerated while another chamber is on stream.

The silica gel is regenerated by washing. The initial washing steps are the desorption steps which are preferably carried out with a C5 to C7 saturated aliphatic hydrocarbon. Higher or lower boiling saturated aliphatic hydrocarbons can be used for the initial wash if so desired. Material which is obtained by washing the silica gel with one of these solvents and subsequent separation therefrom is the preferred fraction which is used for oxidation to obtain the oil additives. Desorption and regeneration of the silica gel is ordinarily carried out at about atmospheric pressure. However, when materials lower boiling than the Css are used as the washing material, it will be necessary to place the silica gel chamber under pressure so as to maintain the wash material in a liquid state. After the desired oil fraction has been obtained by desorption with the saturated aliphatic hydrocarbon, the silica gel is more fully regenerated by washing with an additional solvent fraction, such as benzene, or the like.

After the washing steps have been completed, the silica gel bed is subsequently heated by passing a stream of hot gas such as air, nitrogen, natural gas, or the like therethrough. The hot gas is maintained at a temperature within the rangeof 300 F. and 700 F. Air is not as desirable as theother gases for heating when high temperarates are used, for the reason that flashing might take place in the higher temperatures in the presence of air.

The oil fraction which I utilize for oxidation to obtain the detergent material generally has no fractional part having a refractive index greater than 1.5100 and preferably ,no fractional part having a refractive index greater After the contacting is completed the silica gel is desorbed with normal pentane in three separate washing steps. In subsequent washing steps a portion of benzene is added in progressively larger amounts and a progresisvely smaller amount of normal pentane are used as the wash liquid. Certain characteristics of the oil obtained as the result of each of these washing steps are set forth below in Table I. The data set forth in the column headed Percent Carbon Atoms in Aromatic Rings were calculated in accordance with a procedure set forth by K. van Nes and H. A. van Weston in Aspects of the Constitution of Mineral Oil, Elsevier Publishing Company, Inc.

Table I Percent Percent Refractive Viscosity, Viscosity, Carbon Fraction Charge Color Index Sus.,2l F. Index Atoms in Aromatic Rings 12. 9 Slight blue fluorescence 37. 2 15.4 5.1 2.8 1.6 1.4 1.0 1. 0.8 4.0 10.0 0.-5 3. 5 0.5 O. 5

*Too dark to measure.

than 1.4875. The viscosity index of the fraction obtained by the process of this invention is generally greater than 70 and preferably is at least 100. It is preferred that no fractional part contain more than percent and preferably no more than 5 percent of its carbon atoms in aromatic rings. 7

During the silica gel contacting, the percent of carbon atoms in the aromatic rings, is materially reduced in the preferred fraction when compared to the more aromatic portions of the original charge of the petroleum bright stock. The petroleum fraction obtained by this purification step is subjected to oxidation by means of treating with an oxidizing material such as sulphur trioxide, free oxygen, as in air or pure oxygen. This oxidation step may be carried out at temperatures within the range of between about 390 F. and 620 F. It is preferred to carry out the oxidation step at a temperature within the range of 400 F. and 480 F. The pressure which may be utilized for this oxidation treatment may range from atmospheric up to about 100 p. s. i. g. The oxidation product obtained by the oxidation treatment of the highly refined and purified petroleum fraction is a very high molecular Weight material and has a red color instead of the usual black appearance encountered when the highly refined petroleum fraction is oxidized without first utilizing the purification step of this invention. The various methods of oxidizing the petroleum fraction constitute a part of this invention only to the extent that they are utilized in conjunction with a petroleum fraction defined as the preferred fraction set forth above.

It should be noted that the fraction which I prefer to utilize as the charge stock for the oxidation step of this process cannot be obtained by distillation. In a distillation step' the percent of carbon atoms present in the aromatic rings remains relatively constant for any fraction obtained. The exact manner by which the silica gel reduces the percent of carbon atoms present in the arcmatic rings is not understood. However, the silica gel appears to possess a particular affinity for the aromatics carrying the large number of carbon atoms therewith.

A 250 SAE viscosity propane fractionated and phenol extracted oil is subjected to contact with silica gel at substantially room temperature and atmospheric pressure.

The above data are presented to exemplify the invention and not to unduly limit it. Oxidation products obtained by oxidation of the first two oil fractions are red in color and do not possess the black appearance of the oxidation products obtained'by oxidation of a highly refined petroleum bright stock without the purification steps of this invention. Each of the. successive fractions, when subjected to oxidation, resulted in oxidation products which were successively darker in color.

By the term fractional part, used herein, I intend to include only those fractional parts of the oil product obtained, such as the unadsorbed oil or by Washing the silica gel with one of the wash liquids disclosed hereinbefore and/or by washing with saturated cyclic hydrocarbons preferably in the C5 to C12 range, including side chains.

Various modifications of this invention will be apparent upon study of the accompanying disclosure. It is believed that such modifications are clearly within the spirit and scope of this invention.

I claim:

1. A process for producing oxidized petroleum products which comprises passing a propane-fractionated, phenolextracted petroleum fraction having a viscosity in the range 70 to 700 Saybolt seconds at 210 F. through a bed of silica gel; washing said silica gel with a saturated aliphatic hydrocarbon having a boiling point below that of said petroleum fraction; combining the petroleum fraction obtained by said wash with any petroleum fraction unadsorbed on said silica gel; subjecting the combined petroleum fraction to contact with an oxidizing agent at a temperature within the range of between 390 F. and 620 F.; and recovering resulting oxidation products from the oxidized combined petroleum fraction.

2. The process of claim 1 wherein the combined oil fraction has no fractional part havingmore than 15 percent of its carbon atoms present in aromatic rings.

3. The process of claim 1 wherein the combined oil fraction has no fractional part having more than 5 percent of its carbon atoms present in aromatic rings.

4. A process for producing oxidized petroleum products which comprises passing a propane fractionated, phenolextracted petroleum fraction having a viscosity in the range 70 @790 Saybolt seconds at 210 F. through a bed of silica gel; recovering an unadsorbed oil fraction therefrom; washing said silica gel with a saturated aliphatic hydrocarbon in the C5 to C7 range; combining the petroleum fraction obtained by said wash with said unadsorbed oil fraction; subjecting said combined petroleum fraction to contact with an oxidizing agent at a temperature within the range of between 390 F. and 620 F.; and recovering resulting oxidation products.

5. The process of claim 4 wherein said oxidizing agent is sulfur trioxidc. 1

6. The process of claim 4 wherein said oxidizing agent is free oxygen.

7. The process of claim 4 wherein said oxidation is obtained at a temperature within the range of between 400 F. and 480 F.

8. A process which compnises contacting a propanefractionated, phenol-extracted petroleum oil having a viscosity in the range 70 to 700 Saybolt seconds at 210 F. with adsorbent silica gel to adsorb part of the components of said fraction, oxidizing a nonadsorbed fraction of said oil with an oxidizing agent at an elevated temperature to produce an oxidation product having detergent properties and improved color, and recovering said prodnot.

9. A process which comprises contacting a propanefractionated, phenol-extracted petroleum fraction having a viscosity in the range 70 to 700 Saybolt seconds at 210 F. with adsorbent silica gel under adsorption conditions, oxidizing a nonadsorbed fraction with an oxidizing agent at a temperature in the range from about 390 to about 620 F., and recovering an oxidation product having a red color.

10. A process for producing oxidized petroleum products which comprises passing a propane-fractionated,

phenol-extracted petroleum fraction having a viscosity.

within the range 70 to 700 Saybolt seconds at 210 F. through a bed of silica gel; washing said silica gel with a saturated aliphatic hydrocarbon having a boiling point below that of said petroleum fraction; combining the petroleum fraction obtained by said wash with the fraction remaining unadsorbed on said silica gel and thus obtaining a purified oil, all fractional parts of which have a refractive index at least as small as 1.5100 and a viscosity index of at least subjecting the purified oil to contact with an oxidizing agent at a temperature within the range of between 390 F. and 620 F.; and recovering resulting oxidation products.

11. A process for producing oxidized petroleum products which comprises passing a propane-fractionated, phenol-extracted petroleum fraction having a viscosity within the range to 700 Saybolt seconds at 210 F. through a bed of silica gel; washing said silica gel with a saturated aliphatic hydrocarbon having a boiling point below that of said petroleum fraction; combining the petroleum fraction obtained by said wash with the fraction remaining unadsorbed on said silica gel and thus obtaining a purified oil, all fractional parts of which have a refractive index at least as small as 1.4875 and a viscosity index of at least subject-ing the purified oil to contact with an oxidizing agent at a temperature within the range of between 390 F. and 620 F.; and recovering resulting oxidation products.

12. A process which comprises contacting a propanefractionated, phenol-extracted petroleum fraction having a viscosity in the range 70 to 700 Saybolt seconds at 210 F. with adsorbent silica gel under adsorption conditions. oxidizing a nonadsorbed fraction with air at a temperature in the range from about 390 to about 620 F., and recovering an oxidation product having a red color.

References Cited in the file of this patent UNITED STATES PATENTS 2,352,213 Lieber et al June 27, 1944 2,365,220 Schultz et a1. Dec. 19, 1944 2,447,794 Brewer Aug. 24, 1948 2,572,866 Jones Oct. 30, 1951 2,632,727 Lanneau et al. Mar. 24, 1953 2,674,568 Lillard Apr. 6, 1954 OTHER REFERENCES Stossel Oxidation of Paraflins, Oil and Gas Journal, Sept. 1, 1945, pp. 69 to 73. 

1. A PROCESS FOR PRODUCING OXIDIZED PETROLEUM PRODUCTS WHICH COMPRISES PASSING A PROPANE-FRACTIONATED, PHENOLEXTRACTED PTEROLUEM FRACTION HAVING A VISCOSITY IN THE RANGE 70 TO 700 SAYBOLT SECONDS AT 210* F. THROUGH A BED OF SILICA GEL; WASHING SAID SILICA GEL WITH A SATURATED ALIPHATIC HYDROCARBON HAVING A BOILING POINT BELOW THAT OF SAID PETROLUEM FRACTION; COMBINING THE PETROLEUM FRACTION OBTAINED BY SAID WASH WITH ANY PETROLEUM FRACTION UNADSROBED ON SAID SILICA GEL; SUBJECTING THE COMBINED PETROLEUM FRACTION TO CONTACT WITH AN OXIDIZING AGENT AT A TEMPERATURE WITHIN THE RANGE OF BETWEEN 380* F. AND 620* F.; AND RECOVERING RESULTING OXIDATION PRODUCTS FROM THE OXIDIZED COMBINED PETROLEUM FRACTION. 